1. Field of the Invention
The present invention relates generally to electronic recognition and identification systems for recognizing and identifying electrically-coded objects and more particularly to a system including an electrical network adapted to respond to the frequency of coded electrical resonant circuits.
2. Description of the Prior Art
Electronic recognition and identification systems such as the common lock and key systems presently exist for performing various functions relative to portal control. For example, an individual may carry an electrically-coded identification card (key) for presentation to a reading station when the individual desires to enter a door. If the card carries an appropriate code, responsive identification control signals are generated, which in turn permit the opening of the door.
In another application an object may carry an identification card electrically-coded to identify the object. As the card passes a reading station, the code is read and responsive identification control signals are generated. The identification signals may accordingly be utilized to control associated object processing equipment or, if the object is in transit, the destination of the object.
Examples of prior electronic recognition and identification systems may be found in U.S. Pat. No. 3,752,960 entitled "Electronic Identification and Recognition System", U.S. patent application Ser. No. 363,851 entitled "Improved Electronic Recognition and Identification System" filed May 25, 1973, now U.S. Pat. No. 3,816,718, by Charles A. Walton and assigned to the assignee of the present application, and U.S. Pat. No. 3,842,246 entitled "Recognition and Identification System With Noise Rejection Capabilities" by Robert D. Kohler, David P. Sidlauskas and Charles A. Walton and assigned to the assignee of the present application. U.S. Pat. No. 3,732,465 describes an electronic sensing and actuator system.
In various applications, especially those employing locks and keys, it is desirable to have a lock which may be entered by a group of keys, each of which bears a different code. An example of such an application is typically found in an office environment when doors to a group of offices each have an individual key and lock combination with all of the associated group of keys being capable of operating a lock on a door of a common facility. Generally, the common door has a relatively low security, such as for example the main door, the elevator or the washroom.
This application in which many keys, each associated with a specific door, are able to open a common door is commonly referred to as "maisoning". Though maisoning is commonly realized in mechanical lock and key systems, it is unknown in electronic recognition and identification systems of this type.